JP4830579B2 - Transformer connection circuit, discharge tube lighting circuit, and electronic device - Google Patents

Description

  The present invention relates to a transformer connection circuit in which a plurality of transformers are connected, a discharge tube lighting circuit for lighting a plurality of discharge tubes such as cold cathode tubes, and an electronic device including the discharge tube lighting circuit and the transformer connection circuit.

  Conventionally, as a cold cathode tube (discharge tube) used for a backlight of a large liquid crystal display device or the like, an I-shaped discharge tube, a U-shaped discharge tube in which one long discharge tube is bent at the center, or 2 A pseudo U-shaped discharge tube to which a book I-shaped discharge tube is connected is used. In this type of large-sized liquid crystal display device or the like, usually, the backlight is lit by a plurality of discharge tubes (for example, 10 or more in the case of a backlight for a liquid crystal display having a screen size of 30 to 40 inches) and the discharge tubes. (Refer to Patent Document 1).

  A simple configuration example of a conventional discharge tube lighting circuit will be described with reference to FIG. Here, a discharge tube lighting circuit is shown in which a transformer is connected to both terminals of the pseudo U-shaped discharge tube, and the pseudo U-shaped discharge tube is turned on by the high-voltage AC output of the transformer. Each transformer includes one primary coil and one secondary coil.

  In FIG. 1A, a backlight 101 has a U-shaped discharge tube 102 connected to a discharge tube lighting circuit 105. The U-shaped discharge tube 102 is a pseudo U-shaped discharge tube in which two I-shaped discharge tubes 103A and 103B are connected to each other at one end. The other ends of the I-shaped discharge tubes 103 A and 103 B are connected to power supply terminals 104 A and 104 B of the discharge tube lighting circuit 105. Resonant capacitors C1A and C1B are connected to the secondary sides of the transformers T1A and T1B, respectively. Further, the secondary coils NS of the transformers T1A and T1B are respectively connected to the power supply terminals 104A and 104B in opposite directions so that the input AC voltage has opposite polarity at both ends of the U-shaped discharge tube 102. The primary side coils NP of the transformers T1A and T1B are connected in parallel to the output terminal of the switching circuit 110.

  In the backlight 101, the switching circuit 110 applies a switching voltage (primary side voltage) to the primary side coils NP of the transformers T1A and T1B, and the transformers T1A and T1B change the primary side voltage according to the turns ratio. The voltage is boosted and a predetermined secondary output voltage (AC voltage having an amplitude of 1 to 2 kV) is output. Secondary terminals of opposite polarity are applied to both terminals of the U-shaped discharge tube 102, and the U-shaped discharge tube 102 is driven by a drive voltage of about 2 to 4 kV, which is the sum of the amplitudes of the secondary output voltages. Lights up.

  Although this U-shaped discharge tube requires a high starting voltage at the time of starting (at the start of lighting), it can be lit at a driving voltage lower than the starting voltage during continuous lighting. For this reason, the step-up ratio in the transformer is set low here, and in order to compensate for the voltage shortage at the time of start-up, the resonance capacitance is set on the secondary side of each transformer so as to resonate in series with the leakage inductance of the secondary coil NS. Is inserted. As a result, the U-shaped discharge tube is activated by utilizing the characteristic that the step-up ratio of the transformer is increased in the vicinity of the resonance point of the series resonance.

  Further, another configuration example of the conventional discharge tube lighting circuit will be described with reference to FIGS. Here, the example which comprises a discharge tube lighting circuit using a smaller transformer is shown. Each transformer has a magnetic core and a bobbin that are smaller than the transformer shown in FIG. 1A, and a winding with a thin wire diameter. By this winding with a thin wire diameter, two primary coils and one secondary coil are provided. A side coil is formed. A wire having a small wire diameter has a large resistance value, and heat generation increases when a current similar to that in the past is applied. Therefore, here, it is possible to reduce the wire diameter while suppressing heat generation by connecting two primary coils in parallel to the drive circuit and dispersing the current.

  A backlight 201 shown in FIG. 1B has a U-shaped discharge tube 202 connected to a discharge tube lighting circuit 205. The U-shaped discharge tube 202 is a pseudo U-shaped discharge tube in which two I-shaped discharge tubes 203A and 203B are connected to each other at one end. The other ends of the I-shaped discharge tubes 203A and 203B are connected to power supply terminals 204A and 204B. Resonant capacitors C1A and C1B are connected to the secondary sides of the transformers T1A and T1B, respectively. Further, the secondary coils NS of the transformers T1A and T1B are connected to the power supply terminals 204A and 204B in opposite directions so that the input AC voltage has opposite polarity at both ends of the U-shaped discharge tube 202.

  Here, the transformers T1A and T1B are obtained by providing the primary side coils NP1 and NP2 and the secondary side coil NS on a single magnetic core, respectively. The primary coils NP1 and NP2 of the transformers T1A and T1B are connected in parallel to the output terminal of the switching circuit 210.

  A specific structural example of the transformers T1A and T1B will be described with reference to FIG. (A) is a schematic view of a transformer, and (B) is a cross-sectional view taken along line AA ′ in (A). The transformer T1 is formed by bringing together three magnetic legs of the E-shaped magnetic cores 211A and 211B to form a magnetic path. The center magnetic leg among the three magnetic legs arranged in each of the magnetic cores 211A and 211B is inserted into the tubular bobbin 212. The bobbin 212 has a plurality of partition portions 215 that circulate in the outer peripheral direction, and the primary side coil NP1 and the primary side coil NP2 are provided in the winding region 212A at one end among the plurality of regions partitioned by the partition portion 215. And winding. Further, in the winding region 212B, a secondary coil NS is configured by performing multiple winding for each region finely partitioned by the plurality of partition portions 215 while sequentially pulling the windings. Here, partitioning the winding region 212B suppresses a large potential difference between the overlapping windings.

  In the winding process of the primary coil in the transformer T1, one conductor wire is bent at the center to form two conductor wires, and the conductor wire is bent and wound around the winding region 212A of the bobbin 212. The primary coil NP <b> 1 and the primary coil NP <b> 2 are formed by turning and winding a predetermined number of turns and then cutting the conductor wire at the bent portion. By this process, the primary side coil NP1 and the primary side coil NP2 are simultaneously formed, and the primary side coils NP1 and NP2 have the same wire diameter and number of turns.

The switching circuit 210 shown in FIG. 1B supplies an AC voltage to the I-shaped discharge tubes 203A and 203B through the transformers T1A and T1B having the above-described configuration. The primary side voltages NP1 and NP2 (four primary side coils connected in parallel) of the transformers T1A and T1B are respectively applied with the primary side voltage having the same voltage waveform, and the current flows in a distributed manner.
JP 2005-5059 A

  In the transformer configured as described above, since the bent thin conductor wire is wound around the winding region 212A, the wire diameter and the number of turns of the primary side coils NP1 and NP2 can be made the same. Disturbance is likely to occur, in which case the winding diameter and winding position are shifted, and the winding lengths of the primary side coils NP1 and NP2 may be different from each other. Then, the characteristics such as the inductance value and DC resistance value of the primary side coils NP1 and NP2 may vary.

  Further, the windings in the vicinity of the adjacent ends of the primary side coil and the secondary side coil are irregularly arranged, and the interval between the primary side coil and the secondary side coil is also irregular. The degree of coupling between the coil and the secondary side coil is greatly different for each coil, and the primary side coils are strongly coupled to each other, thereby generating a large circulating current. Due to these factors, current concentration may occur in a specific coil, leading to abnormal heat generation.

  Furthermore, in a discharge tube lighting circuit using a plurality of transformers, even if products of the same part number are used for each transformer, characteristic variations occur for each transformer, thereby causing current concentration on the primary side of a specific transformer. Or, the output voltage waveform on the secondary side of a specific transformer could not be made desired. This is a particularly serious problem in an electronic device (such as a liquid crystal display device) equipped with a large number of transformers, and has become a factor of weakening the reliability of the transformer connection circuit and the discharge tube lighting circuit.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the reliability of a transformer connection circuit and a discharge tube lighting circuit composed of a transformer having a thin wire diameter, suppress current concentration, and reliably obtain a desired output voltage waveform. It is to provide a connection circuit and a discharge tube lighting circuit.

In order to solve the above problems, a transformer connection circuit according to the present invention winds a plurality of coils from an inner layer to an outer layer so that each coil forms a layer in a first winding region of a magnetic core. A plurality of laminated transformers configured by winding a coil different from the coil in the second winding region of the magnetic core, and sequentially from the inner layer side or the outer layer side of the first winding region of the first laminated transformer. The selected coil and the coil selected in the reverse order to the first laminated transformer from the outer layer side or the inner layer side of the first winding region of the second laminated transformer are connected in series, respectively, A plurality of series coil circuits having the same total winding length of the included coils are provided, and the plurality of series coil circuits are connected in parallel .

  Since only a single coil is wound on each layer of the first winding region of the laminated transformer in this way, the primary side coil can be configured without any collapse or turbulence. The diameter and winding position can be made predetermined. Accordingly, the winding length of each coil can be set to a predetermined value, and the inductance value and DC resistance value of each coil can be reliably set to a predetermined value, thereby eliminating characteristic variations between products.

  However, in such a transformer, the winding diameter and the winding length are different for each layer, and the inductance value and the DC resistance value of the coil for each layer are predetermined values. That is, the inner layer coil has a short winding length and a small inductance value and a DC resistance value, and the outer layer coil has a long winding length and a large inductance value and a DC resistance value. Therefore, if these coils are directly connected in parallel to the drive circuit, current concentration will occur in the inner layer coil having a small inductance value and DC resistance value.

  Therefore, a plurality of transformer coils are connected to form a current path, and each current path is connected to a drive circuit. Then, the total winding length of the plurality of coils included in any of the current paths is made equal to the total winding length of the plurality of coils included in the other current paths. For example, in the case of a transformer having a two-layer structure, an inner layer coil of the first transformer and an outer layer coil of the second transformer are connected to form one current path, and the outer layer coil of the first transformer Another current path is formed by connecting with the inner layer coil of the second transformer, and these current paths are connected in parallel to the drive circuit. With such a configuration, the total winding length, the total inductance value, and the total DC resistance value of the plurality of current paths can be made equal, and the currents flowing through the respective current paths can be made equal. Therefore, current concentration does not occur in a specific winding of the transformer, and the reliability of the transformer connection circuit and the discharge tube lighting circuit can be improved.

And since the coil of a some transformer is connected in series and a series coil circuit is comprised and each series coil circuit is connected to a drive circuit in parallel, each series coil circuit becomes a current path. With such a configuration, the total winding length, the total inductance value, and the total DC resistance value of all the series coil circuits can be made equal, and the currents flowing through the series coil circuits can be made equal. Therefore, current concentration does not occur in a specific winding of the transformer, and the reliability of the transformer connection circuit and the discharge tube lighting circuit can be improved.

The discharge tube lighting circuit of the present invention is a discharge tube lighting circuit comprising the transformer connection circuit and a switching circuit, wherein the plurality of series coil circuits of the transformer connection circuit are parallel to the switching circuit, respectively. The terminals of the discharge tube are respectively connected to the coils wound around the second winding region of the first laminated transformer and the second laminated transformer .

  An electronic device according to the present invention includes the transformer connection circuit or the discharge tube lighting circuit.

  According to the present invention, since there is no coil collapse or turbulence and current concentration in the primary coil of the transformer is suppressed, a transformer connection circuit, a discharge tube lighting circuit, an electronic circuit with low heat generation, low loss, and high reliability The device can be configured.

  Hereinafter, a discharge tube lighting circuit for lighting one pseudo U-shaped discharge tube will be described as an example of the first embodiment. In addition, in the backlight used for the liquid crystal display device, a configuration in which several to ten or more U-shaped discharge tubes are actually provided is generally used, but here, a simple configuration to avoid complicated explanation, A description will be given of a configuration in which one pseudo U-shaped discharge tube is provided. In the following description, a pseudo U-shaped discharge tube is used. However, the present invention is not limited to this, and not only a simple U-shaped discharge tube, but also an I-shaped discharge tube, two or more I-shaped discharge tubes are used. This can be implemented by using a type discharge tube.

  FIG. 3A is a diagram showing a circuit configuration of the discharge tube lighting circuit of the present embodiment. The backlight 1 is used for a liquid crystal display device, and includes a U-shaped discharge tube 2 and a discharge tube lighting circuit 5. The U-shaped discharge tube 2 is a pseudo U-shaped discharge tube composed of two I-shaped discharge tubes 3A and 3B. The terminals of the U-shaped discharge tube 2 are connected to the discharge tube lighting circuit 5 through power supply terminals 4A and 4B. Specifically, the I-shaped discharge tube 3A is connected to the transformer T1A via the power supply terminal 4A, and the I-shaped discharge tube 3B is connected to the transformer T1B via the power supply terminal 4B. The I-shaped discharge tubes 3A and 3B are arranged at equal intervals on the back surface of a liquid crystal panel (not shown).

  The discharge tube lighting circuit 5 is an inverter provided on the mounting board, and generates an AC voltage having a predetermined frequency from a DC voltage supplied from a power source (not shown) of the electronic device. The discharge tube lighting circuit 5 includes capacitors C1A and C1B, a transformer connection circuit 7, and a switching circuit 10.

  The switching circuit 10 of the discharge tube lighting circuit 5 generates a rectangular wave-shaped switching voltage from a DC voltage supplied from a power source of the electronic device, and applies this switching voltage to the series coil circuits 6A and 6B. Specifically, the switching voltage is controlled using a half-bridge type or full-bridge type switching circuit so as to obtain a rectangular wave with a 50% on-duty ratio. The details of this control are not related to the essence of the present invention, so the description is omitted here, and general switching control may be performed, and the on-duty ratio is not limited to 50%.

  The transformer connection circuit 7 of the discharge tube lighting circuit 5 includes small transformers T1A and T1B having primary coils NP1 and NP2 and a secondary coil NS, respectively. Each of the transformers T1A and T1B is a laminated transformer, and each of the primary side coils NP1 and NP2 is alternately connected to constitute series coil circuits 6A and 6B. The series coil circuit 6A is formed by connecting a winding end of the primary side coil NP2 of the transformer T1A and a winding start end of the primary side coil NP1 of the transformer T1B in series. The series coil circuit 6B is formed by connecting a winding end of the primary side coil NP1 of the transformer T1A and a winding start end of the primary side coil NP2 of the transformer T1B in series. These series coil circuits 6A and 6B are connected in parallel to the switching circuit 10, respectively.

  Here, a specific detailed configuration of the transformers T1A and T1B will be described with reference to FIG. Here, only a cross-sectional view is shown without particularly showing an overview of the transformer, but this overview of the transformer is the same as that of the conventional configuration shown in FIG. Only the winding structure is different.

  Specifically, the transformer T1 is formed by bringing together three magnetic legs of the magnetic cores 11A and 11B (E-shaped) to form a magnetic path. Of the three magnetic legs of the magnetic cores 11 </ b> A and 11 </ b> B, the central magnetic leg shown in the figure is inserted into the tubular bobbin 12. The bobbin 12 has a plurality of partition portions 15A to 15F that circulate in the outer peripheral direction, and the primary side coil NP1 and the primary side coil NP2 are wound around the winding region 12A partitioned by the partition portions 15A-15B. Yes. Further, in the winding region 12B composed of the partition portions 15B-15C, 15C-15D, 15D-15E, and 15E-15F, the windings are sequentially drawn out to the regions between the partition portions, and the partition portions 15B-15C, A secondary coil NS is formed by winding a plurality of windings for each region between 15C-15D, 15D-15E, and 15E-15F. Due to the configuration of the secondary coil NS, a large potential difference is suppressed between the overlapping windings in each of the regions between the partition portions 15B-15C, 15C-15D, 15D-15E, and 15E-15F.

  The primary side coil NP1 and the primary side coil NP2 wound around the winding region 12A are each a single conductor wire wound around the winding region 12A of the bobbin 12 in a single layer. The primary coil NP2 layer is provided on the side coil NP1 layer. Each of the primary side coils NP1 and NP2 has the same wire diameter and number of turns, the primary side coil NP1 provided in the inner layer is small, and the primary side coil NP2 provided in the outer layer is large. It is. Therefore, the winding length of the primary side coil NP1 is short, and the winding length of the primary side coil NP2 is long. In this transformer, the primary side coil is individually wound around each layer of the winding region 12A, so that each coil can be wound without being collapsed or disturbed, and the winding diameter and winding position of each coil can be accurately determined. It can be made predetermined. Accordingly, the winding length of each coil can be accurately set to a predetermined value, and the inductance value and DC resistance value of each coil can be set to a predetermined value accurately.

  The secondary side coil is wound with the same number of multiple turns as the plurality of primary side coils in the primary side winding region 12A (here, it is a double winding, but the number of turns is changed in accordance with the discharge tube. And the winding interval between the primary side coil and the secondary side coil is equal to the width dimension of the partition portion 15B. And the coupling | bonding of each primary side coil NP1, NP2 and the secondary side coil NS is made constant. With such a configuration, there is no variation in characteristics between products of a plurality of transformers, and the output voltage characteristics of each transformer are stabilized.

The series coil circuits 6A and 6B shown in FIG. 3A are constituted by primary coils NP1 and NP2 of the transformers T1A and T1B having the above-described configuration, respectively. Are connected to the primary coil NP1 in the inner layer of the transformer T1B, and the series coil circuit 6B connects the primary coil NP1 in the inner layer of the transformer T1A and the primary coil NP2 in the outer layer of the transformer T1B. It is a thing. When the number of turns of each of the series coil circuits 6A and 6B is n, the winding lengths Lnp1 and Lnp2 of the primary side coils NP1 and NP2 of each transformer are expressed by the following equations.
Lnp1 = nπR
Lnp2 = nπ (R + A)
Here, the circumference ratio is π, the winding diameter of the primary coil NP1 (the outer diameter of the bobbin and the wire diameter of the winding) is R, and the wire diameter of the winding is A. Therefore, the total winding length L of each of the series coil circuits 26A to 26C is expressed by the following equation.
L = Lnp1 + Lnp2 = Lnp2 + Lnp1
= 2nπR + nπA
Thus, the total winding length L of each of the series coil circuits 6A and 6B is equal.

  An AC voltage is supplied from the switching circuit 10 to the I-shaped discharge tubes 3A and 3B via the transformers T1A and T1B configured as described above. Since the series coil circuits 6A and 6B are connected in parallel to each other, a switching voltage having the same voltage waveform is applied to each. This switching voltage is distributed to the primary side coils NP1 and NP2 constituting each series coil circuit, the primary side voltage NP1 is applied to the primary side coil NP1 of each series coil circuit, and 1 is applied to the primary side coil NP2. A secondary voltage V2 is applied. Since each series coil circuit 6A, 6B has the same wire diameter and the same total winding length, the current I1 flowing through the series coil circuit 6A and the current I2 flowing through the series coil circuit 6B have the same current value. Therefore, current concentration does not occur in a specific winding.

  The transformer T1A has the winding start end of the secondary coil NS as the ground, the winding end as the power supply terminal 4A of the I-shaped discharge tube 3A, and the transformer T1B has the winding end of the secondary coil NS as the ground. In addition, the winding start end is connected to the power supply terminal 4B of the I-shaped discharge tube 3B. By configuring the transformers T1A and T1B in this way, the primary side voltages NP1 and NP2 of the primary side coils NP1 and NP2 are respectively turned from the secondary side coils NS of the transformers T1A and T1B. A predetermined secondary output voltage (1 to 2 kV) boosted according to the number of turns of the secondary coil NS is output, and AC output voltages having different polarities are applied to both ends of the U-shaped discharge tube 2. .

  FIG. 4 shows the voltage waveform of the secondary output voltage of each transformer. (A) is a voltage waveform of the secondary output voltage Va of the transformer T1A. (B) is a voltage waveform of the secondary output voltage Vb of the transformer T1B. The secondary output voltages Va and Vb of the transformers T1A and T1B respectively show sinusoidal waveforms having the same frequency, and the secondary output voltages Va and Vb of the transformers T1A and T1B connected to the power supply terminals 4A and 4B. Indicates sinusoidal waveforms with opposite polarities, that is, 180 degrees out of phase. Secondary output voltages Va and Vb having opposite polarities are applied to both terminals of the U-shaped discharge tube 2, respectively. Therefore, the voltage between both terminals becomes a voltage amplitude (2 to 4 kV) obtained by adding the voltage amplitudes (1 to 2 kV) between the secondary side output voltages Va and Vb, which is twice the secondary side output voltages Va and Vb. A driving voltage is applied. The U-shaped discharge tube 2 is supplied with secondary output voltages Va and Vb independent from the power supply terminals 4A and 4B, respectively, and the U-shaped discharge tube 2 is lit.

  The capacitors C1A and C1B of the discharge tube lighting circuit 5 are connected between the secondary coil NS of the transformers T1A and T1B and the ground, respectively. These capacitors C1A and C1B resonate in series with the leakage inductances of the transformers T1A and T1B when the backlight 1 is started, and apply a high voltage necessary for starting and lighting to the I-shaped discharge tubes 3A and 3B. The capacitors C1A and C1B are not necessarily provided in the discharge tube lighting circuit 5, and when the frequency of the secondary output voltage is high, the secondary coil NS of each transformer is changed to the capacitance of the capacitors C1A and C1B. It is also possible to obtain a resonance voltage using parasitic capacitance distributed around the power supply terminals 4A and 4B and the U-shaped discharge tube 2.

  Here, a current detection circuit (not shown) is provided between the secondary side ground of the transformer T1A and the secondary side ground of the transformer T1B to detect the tube current of the U-shaped discharge tube 2, and the tube current. The switching voltage of the switching circuit 10 may be controlled so as to be stabilized. Since the configuration for stabilizing the tube current is not related to the essence of the present invention, the description is omitted here and a general configuration may be used.

  With the above configuration, the backlight 1 and the discharge tube lighting circuit 5 of the present embodiment turn on the U-shaped discharge tube 2. Note that the capacitances of the capacitors C1A and C1B are adjusted so that the output characteristics of the transformers T1A and T1B are substantially matched.

  As described above, according to the discharge tube lighting circuit 5 of the present embodiment, as the transformers T1A and T1B used in the transformer connection circuit 7, the laminated transformer in which the primary side coils are laminated is used. Therefore, the primary side coil provided in each layer is used. Predetermined characteristics can be obtained, and characteristic variations between the transformers T1A and T1B can be almost eliminated. Further, since the primary coils NP1 and NP2 of the transformers T1A and T1B are alternately connected to form the series coil circuits 6A and 6B, the total winding length and the total inductance value of each of the series coil circuits 6A and 6B. The total DC resistance values can be made equal to each other, and the current values flowing through them can be made the same to avoid current concentration. Even in this case, since the transformers T1A and T1B are supplied with the same primary side voltage and input current, the secondary side output voltages can be made equal. Therefore, the reliability of the transformer connection circuit and the discharge tube lighting circuit can be improved.

  Next, the circuit configuration of the discharge tube lighting circuit according to the second embodiment of the present invention will be described with reference to FIG. Here, each transformer includes three primary coils and one secondary coil, and distributes current to the three primary coils to flow current.

  The backlight 21 is used in a liquid crystal display device, and includes a U-shaped discharge tube 22 and a discharge tube lighting circuit 25. The U-shaped discharge tube 22 is a pseudo U-shaped discharge tube composed of two I-shaped discharge tubes 23A and 23B. The terminals of the U-shaped discharge tube 22 are connected to the discharge tube lighting circuit 25 via power supply terminals 24A and 24B.

  The discharge tube lighting circuit 25 is an inverter provided on the mounting board, and generates an AC voltage having a predetermined frequency from a DC voltage supplied from a power source (not shown) of the electronic device. The discharge tube lighting circuit 25 includes capacitors C1A and C1B, a transformer connection circuit 27, and a switching circuit 30.

  The transformer connection circuit 27 of the discharge tube lighting circuit 25 includes transformers T1A and T1B having primary coils NP1, NP2 and NP3 and a secondary coil NS, respectively. Each of the transformers T1A and T1B is a laminated transformer. The primary side coils NP1 and NP3 are alternately connected to each other to connect the series coil circuits 26A and 26C, and the primary side coils NP2 of the transformers T1A and T1B are connected to each other. Thus, the series coil circuit 26B is configured.

  The series coil circuit 26A is formed by connecting the winding end of the primary side coil NP3 of the transformer T1A and the winding start end of the primary side coil NP1 of the transformer T1B in series. The series coil circuit 26B is formed by connecting the winding end of the primary side coil NP2 of the transformer T1A and the winding start end of the primary side coil NP2 of the transformer T1B in series. The series coil circuit 26C is formed by connecting the winding end of the primary side coil NP1 of the transformer T1A and the winding start end of the primary side coil NP3 of the transformer T1B in series. These series coil circuits 26 </ b> A to 26 </ b> C are connected in parallel to the switching circuit 30.

  The specific detailed configuration of the transformers T1A and T1B is the same as that of the transformer shown in the first embodiment, and only the winding structure of the primary side coil is different. The primary side coils NP1 to NP3 are each formed by winding a single conductor wire in a primary winding region on the primary side coil NP1 on the layer of the primary side coil NP1. A layer is provided, and the layer of the primary coil NP3 is provided on the layer of the primary coil NP2. Each of the primary side coils NP1 to NP3 has the same wire diameter and number of turns, the primary side coil NP1 provided in the inner layer has a small winding diameter, the primary side coil NP3 provided in the outer layer has a large winding diameter, and the intermediate layer The winding diameter of the primary side coil NP2 provided in is equal to the average value of the winding diameters of the primary side coil NP1 and the primary side coil NP3. Therefore, the winding length is increased in the order of the primary side coil NP1, the primary side coil NP2, and the primary side coil NP3. In this transformer, the primary coil is individually wound on each layer of the winding region, so that each coil can be wound without being collapsed or disturbed, and the winding diameter and winding position of each coil can be accurately determined. Can be a predetermined one. Accordingly, the winding length of each coil can be accurately set to a predetermined value, and the inductance value and DC resistance value of each coil can be set to a predetermined value accurately.

The series coil circuits 26A, 26B, and 26C are configured by the primary side coils NP1, NP2, and NP3 of the transformers T1A and T1B having the above-described configuration, respectively. The primary coil NP1 in the inner layer of T1B is connected, and the series coil circuit 26B connects the primary coil NP2 in the intermediate layer of the transformer T1A and the primary coil NP2 in the intermediate layer of the transformer T1B. The series coil circuit 26C is formed by connecting the primary coil NP1 in the inner layer of the transformer T1A and the primary coil NP3 in the outer layer of the transformer T1B. When the number of turns of each of the series coil circuits 26A, 26B, and 26C is n, the winding lengths Lnp1, Lnp2, and Lnp3 of the primary side coils NP1 to NP3 of each transformer are expressed by the following equations.
Lnp1 = nπR
Lnp2 = nπ (R + A)
Lnp3 = nπ (R + 2A)
Here, the circumference ratio is π, the winding diameter of the primary coil NP1 (the outer diameter of the bobbin and the wire diameter of the winding) is R, and the wire diameter of the winding is A. Therefore, the total winding length L of each of the series coil circuits 26A to 26C is expressed by the following equation.
L = Lnp1 + Lnp3 = Lnp2 + Lnp2 = Lnp3 + Lnp1
= 2nπR + 2nπA
Thus, the total winding length L of each series coil circuit 26A-26C is equal.

  An AC voltage is supplied from the switching circuit 30 to the I-shaped discharge tubes 23A and 23B via the transformers T1A and T1B configured as described above. Since the series coil circuits 26A, 26B, and 26C are connected to each other in parallel, a switching voltage having the same voltage waveform is applied to each. This switching voltage is distributed to the primary side coils NP1, NP2 and NP3 constituting each series coil circuit, and the primary side voltage V1 is applied to the primary side coil NP2 in the primary side coil NP1 of each series coil circuit. The primary side voltage V2 is applied to the primary side coil NP3, and the primary side voltage V3 is applied to the primary side coil NP3. Since each series coil circuit 26A, 26B has the same wire diameter and the same total winding length, the current I1 flowing through the series coil circuit 26A, the current I2 flowing through the series coil circuit 26B, and the current I3 flowing through the series coil circuit 26C. And have the same current value. Therefore, current concentration does not occur in a specific winding.

  From the secondary coil NS of each transformer T1A, T1B, the primary voltage of the primary coils NP1, NP2, NP3, the number of turns of the primary coil NP1, NP2, NP3, and the number of turns of the secondary coil NS, respectively. A predetermined secondary output voltage (1-2 kV) boosted accordingly is output, and alternating output voltages having different polarities are applied to both ends of the U-shaped discharge tube 22.

  With the above configuration, the discharge tube lighting circuit 25 of the present embodiment lights the U-shaped discharge tube 22.

  As described above, according to the discharge tube lighting circuit 25 of the present embodiment, a laminated transformer in which a larger number of primary coils are laminated is used as the transformers T1A and T1B. Therefore, the primary coils provided in each layer have predetermined characteristics. And variations in characteristics between the transformers T1A and T1B can be almost eliminated. Further, by configuring the series coil circuits 26A, 26B, and 26C to have the same total winding length, the total inductance value and the total DC resistance value can be made equal to each other, and the current values flowing through the series coil circuits 26A, 26B, and 26C can be made the same. , Current concentration can be avoided. Even in this case, since the transformers T1A and T1B are supplied with the same primary side voltage and input current, the secondary side output voltages can be made equal. Therefore, the reliability of the transformer connection circuit and the discharge tube lighting circuit can be improved. Thus, the present invention can be implemented regardless of the number of layers if a transformer having a laminated structure is used.

  Next, the circuit configuration of the discharge tube lighting circuit according to the third embodiment of the present invention will be described with reference to FIG. Here, a discharge tube lighting circuit for lighting four U-shaped discharge tubes with six transformers is shown.

  In this embodiment, the discharge tube lighting circuit is configured using two types of transformers having different product numbers. Specifically, the transformers T2A to T2D configured by one primary coil and one secondary coil, the two primary coils and one secondary coil shown in the first embodiment Transformers T1A and T1B configured by The transformers T1A and T1B are configured to flow current by being distributed to two primary coils.

  The backlight 41 is used for a liquid crystal display device, and includes U-shaped discharge tubes 42 </ b> A to 42 </ b> D and a discharge tube lighting circuit 45. The U-shaped discharge tube 42A is I-shaped discharge tubes 43A and 43B, the U-shaped discharge tube 42B is I-shaped discharge tubes 43C and 43D, and the U-shaped discharge tube 42C is I-shaped discharge tubes 43E and 43F. The U-shaped discharge tube 42D is a pseudo U-shaped discharge tube made up of I-shaped discharge tubes 43G and 43H. The U-shaped discharge tubes 42A and 42B are connected to the discharge tube lighting circuit 45 via the connector 48A, and the U-shaped discharge tubes 42C and 42D are connected to the discharge tube lighting circuit 45 via the connector 48B. Specifically, the terminal of the I-shaped discharge tube 43A is connected to the transformer T2A of the discharge tube lighting circuit 45 via the power supply terminal 44A provided on the connector 48A, and the terminal of the I-shaped discharge tube 43B is connected to the I-shaped discharge tube 43B. The terminal of the discharge tube 43C is connected to the transformer T1A of the discharge tube lighting circuit 45 via the power supply terminal 44B provided on the connector 48A, and the terminal of the I-shaped discharge tube 43D is the power supply terminal provided on the connector 48A. 44C is connected to the transformer T2B of the discharge tube lighting circuit 45, and the terminal of the I-shaped discharge tube 43E is connected to the transformer T2C of the discharge tube lighting circuit 45 via the power supply terminal 44D provided on the connector 48B. The terminal of the I-shaped discharge tube 43F and the terminal of the I-shaped discharge tube 43G are connected to the transformer T1B of the discharge tube lighting circuit 45 via the power supply terminal 44E provided on the connector 48B. Terminal-shaped discharge tube 43H is connected to the transformer T2D of discharge tube lighting circuit 45 via the power supply terminals 44F provided on the connector 48B.

  Here, the power supply terminal 44B constitutes a common electrode for commonly connecting the terminals of the U-shaped discharge tubes 42A and 42B. The power supply terminal 44E also constitutes a common electrode for commonly connecting the terminals of the U-shaped discharge tubes 42C and 42D. In the following description, the power supply terminals 44A, 44C, 44D, and 44F are referred to as independent electrodes for comparison with the names of the common electrodes. In this embodiment, the terminals of the U-shaped discharge tube are connected in the connector. However, the terminals may be connected on the mounting board instead of in the connector.

  The discharge tube lighting circuit 45 is an inverter provided on the mounting board, and generates an AC voltage having a predetermined frequency from a DC voltage supplied from a power source (not shown) of the electronic device. The discharge tube lighting circuit 45 includes capacitors C1A to C1F, a transformer connection circuit 47, and a switching circuit 50.

  The transformer connection circuit 47 of the discharge tube lighting circuit 45 includes transformers T1A and T1B composed of primary coils NP1 and NP2 and a secondary coil NS, and transformers T2A to T2D composed of a primary coil NP and a secondary coil NS. The primary side coils NP1 and NP2 of the transformers T1A and T1B are alternately connected to form series coil circuits 46A and 46B, and the series coil circuits 46A and 46B are connected in parallel to the switching circuit 50, respectively. The primary coils NP of the transformers T2A to T2D are also connected to the switching circuit 50 in parallel. The series coil circuit 46A is formed by connecting the winding end of the primary side coil NP2 of the transformer T1A and the winding start end of the primary side coil NP1 of the transformer T1B in series. The series coil circuit 46B is formed by connecting the winding end of the primary side coil NP1 of the transformer T1A and the winding start end of the primary side coil NP2 of the transformer T1B in series.

  The specific detailed configuration of the transformers T1A and T1B is the same as that of the transformer shown in the first embodiment. The primary side coils NP1 and NP2 are each formed by winding a single conductor wire in a primary winding region on the primary side coil NP1 on the layer of the primary side coil NP1. It is the structure which provided the layer. Accordingly, the primary side coils NP1 and NP2 have the same wire diameter and number of turns, the primary side coil NP1 provided in the inner layer is small, and the primary side coil NP2 provided in the outer layer is large. It is. Therefore, the winding length becomes longer in the order of the primary side coils NP1 and NP2. In this transformer, the primary side coil is individually wound around each layer of the winding region, so that each coil can be wound without being collapsed or disturbed, and the winding diameter and winding position of each coil can be accurately determined. It can be made predetermined. Accordingly, the winding length of each coil can be accurately set to a predetermined value, and the inductance value and DC resistance value of each coil can be set to a predetermined value accurately.

  The series coil circuits 46A and 46B are configured by the primary side coils NP1 and NP2 of the transformers T1A and T1B having the above-described configuration. The series coil circuit 46A includes the primary side coil NP2 of the outer layer of the transformer T1A and the inner layer of the transformer T1B. The primary coil NP1 is connected, and the series coil circuit 46B is a connection between the primary coil NP1 in the inner layer of the transformer T1A and the primary coil NP2 in the outer layer of the transformer T1B. Therefore, the total winding lengths of the series coil circuits 46A and 46B are equal.

  Further, the winding start end of the secondary coil NS of the transformers T1A and T1B is connected to the common electrode, and the winding end end is directly connected to the ground. On the other hand, in the transformers T2A to T2D, the winding end of the secondary coil NS is connected to an independent electrode, and the winding start is connected to the ground.

  The capacitors C1A to C1F of the discharge tube lighting circuit 45 are connected between the secondary side coil NS of the transformers T1A, T1B, and T2A to T2D and the ground.

  In addition, a current detection circuit (not shown) is provided between the transformers T1A and T1B connected to the common electrode, the transformers T2A to T2D connected to the independent electrodes, and between each secondary coil NS and the ground, and is U-shaped. The tube currents of the type discharge tubes 42A to 42D may be detected to stabilize the tube current. Since the configuration for stabilizing the tube current is not related to the essence of the present invention, the description is omitted here and a general configuration may be used.

  Further, it is preferable that the wire diameter of the secondary coil NS of the transformers T1A and T1B connected to the common electrode is larger than the wire diameter of the secondary coil NS of the other transformers T2A to T2D. It is preferable if the core cross-sectional area of T1B is larger than the core cross-sectional areas of the other transformers T2A to T2D. If comprised in this way, the copper loss by the secondary side coil NS of the transformers T1A and T1B through which a synthetic current flows, the iron loss by the core can be suppressed, and the temperature rise can be suppressed.

Next, the operation when the backlight 41 is continuously turned on will be described.
An AC voltage is supplied from the switching circuit 50 to the power supply terminal 44B to the I-shaped discharge tubes 43B and 43C through the transformer T1A having the above configuration. Further, an AC voltage is supplied to the power supply terminal 44F to the I-shaped discharge tubes 43F and 43G via the transformer T1B. Furthermore, an AC voltage is supplied to power supply terminals 44A, 44C, 44D, and 44F to the I-shaped discharge tubes 43A, 43D, 43E, and 43H, respectively, through transformers T2A to T2D.

  Specifically, the switching circuit 50 switches a DC voltage supplied from the power supply unit of the electronic device by a switching circuit (not shown) such as a half bridge type to generate a rectangular waveform switching voltage. Then, this switching voltage is applied to each of the series coil circuits 46A and 46B and the primary side coils NP of the transformers T2A to T2D.

  Since the primary coil NP of the series coil circuits 46A and 46B and the transformers T2A to T2D are connected in parallel to each other, the switching voltage V3 having the same voltage waveform is applied to each. The switching voltage V3 is distributed to the primary side coils NP1 and NP2 constituting the series coil circuits 46A and 46B, and the primary side voltage V1 is applied to the primary side coil NP1 of each series coil circuit. The primary side voltage V2 is applied to. Since each series coil circuit 46A, 46B has the same wire diameter and the same total winding length, the current I1 flowing through the series coil circuit 46A and the current I2 flowing through the series coil circuit 46B have the same current value. Therefore, current concentration does not occur in a specific winding.

  The secondary side coil NS of each transformer T1A, T1B has a predetermined secondary side output boosted according to the primary side voltage and the number of turns of the primary side coil NP1, NP2 and the number of turns of the secondary side coil NS, respectively. Output voltage. Furthermore, the secondary side coil NS of the transformers T2A to T2D has a predetermined secondary side output voltage boosted according to the primary side voltage and the number of turns of the primary side coil NP and the number of turns of the secondary side coil NS, respectively. Output. Specifically, the excitation current flows from the winding start end to the winding end end of the primary coil during the positive voltage output period of the primary voltage. As a result, the magnetic flux of the core of each transformer increases with time, and a current flows through each secondary coil NS from the winding end to the winding start end. On the other hand, during the negative voltage output period of the primary side voltage, the magnetic flux of the core of each transformer decreases with time, and a current flows through the secondary side coil NS from the winding start end to the winding end end. Since the transformer T1A and the transformer T1B have their winding start ends and winding end ends connected in reverse to the other transformers T2A to T2D, they output a secondary output voltage having a polarity opposite to that of the other transformers T2A to T2D. To do. Further, since the I-shaped discharge tubes 43B and 43C and the I-shaped discharge tubes 43F and 43G are connected to the common electrode, the transformer T1A and the transformer T1B connected to the common electrode have a transformer T2A connected to an independent electrode. Twice as much combined current flows as to T2D.

FIG. 7 shows the voltage waveform of the secondary output voltage of each transformer. (A) is a voltage waveform of the secondary side output voltage Va of the transformer T2A. (B) is a voltage waveform of the secondary output voltage Vb of the transformer T1A. (C) is a voltage waveform of the secondary output voltage Vc of the transformer T2B.
The secondary output voltages Va to Vc of the transformers T2A, T1A, and T2B each have a sine wave waveform having the same frequency, and the secondary output voltages Va and Vc of the transformer T2A and the transformer T2B connected to the independent electrodes are respectively A sinusoidal waveform with the same phase is shown. Further, the secondary output voltage Vb of the transformer T1A connected to the common electrode shows a sine wave waveform that is opposite in polarity to the secondary output voltages Va and Vc, that is, whose phase is shifted by 180 degrees. Note that the voltage waveforms of the secondary output voltages of the transformers T1B, T2C, and T2D are the same as the voltage waveforms Va to Vc of the secondary output voltages of the transformers T1A, T2A, and T2B, respectively.

  Secondary output voltages Va and Vb having opposite polarities are applied to both terminals of the U-shaped discharge tube 42A, respectively. Therefore, the voltage between both terminals becomes a voltage amplitude (2 to 4 kV) obtained by adding the voltage amplitudes (1 to 2 kV) between the secondary side output voltages Va and Vb, which is twice the secondary side output voltages Va and Vb. A driving voltage is applied. Similarly, the U-shaped discharge tubes 42B, 42C, 42D are each applied with a secondary output voltage of opposite polarity to both terminals, and a high drive voltage is applied between both terminals.

  A single secondary output voltage Vb is applied from the common electrode to the U-shaped discharge tubes 42A and 42B, but the secondary output voltage Va or the secondary output voltage Vc applied to the independent electrode is U-shaped. Since the discharge tubes 42A and 42B are independent of each other, the U-shaped discharge tubes 42A and 42B can be turned on even when the U-shaped discharge tubes 42A and 42B are connected in parallel to the common electrode. Further, the U-shaped discharge tubes 42C and 42D can be similarly turned on.

  Capacitors C1A to C1F resonate in series with the respective leakage inductances of T1A, T1B, and T2A to T2D when the backlight is activated, and apply a high voltage necessary for activation and lighting to U-shaped discharge tubes 42A to 42D. The capacitors C1A to C1F are not necessarily provided in the discharge tube lighting circuit 45, and when the frequency of the secondary output voltage is high, the secondary coils of each transformer are connected to the vicinity of the connectors 48A and 48B and the U-shape. It is also possible to obtain a resonance voltage by using parasitic capacitance distributed in the discharge tube instead of the capacitors C1A to C1F.

  In this way, the mounting area of the transformer and the capacitor can be reduced with a simple configuration using only a number (3/4) of high-voltage transformers and resonance capacitors smaller than the number of terminals of the discharge tube. Therefore, even if the area of the mounting board of the discharge tube lighting circuit is the same, more discharge tubes can be arranged as the backlight. In that case, a larger liquid crystal display device can be configured. In addition, since the number of parts of the high-voltage output unit that requires high reliability is reduced, the reliability of the high-voltage output unit is higher than in the past.

  Also, two U-shaped discharge tubes can be connected together in a single connector. Conventionally, a separate connector is required for each U-shaped discharge tube in order to maintain insulation between adjacent terminals of the U-shaped discharge tubes. However, in this configuration, even if the terminals of different U-shaped discharge tubes are connected, for example, the power supply terminals 44B and 44C, which are common electrodes, are connected in an adjacent state, so that the terminals of the different U-shaped discharge tubes are connected to each other. Even if two U-shaped discharge tubes are connected to a single connector, insulation can be secured. With this configuration, the number of connectors as the entire discharge tube lighting circuit can be reduced, the connection work process can be simplified, and the number of work processes can be reduced.

  According to the discharge tube lighting circuit 45 of the present embodiment, since the transformers T1A and T1B used in the transformer connection circuit 47 have a laminated primary coil, there is no characteristic variation between the transformers T1A and T1B. In addition, the primary coil provided in each layer can have predetermined characteristics. Further, since the primary side coils NP1 and NP2 of the transformers T1A and T1B are alternately connected to form the series coil circuits 46A and 46B, the total winding length and the total inductance value of each of the series coil circuits 46A and 46B. The total DC resistance values can be made equal to each other, and the current values flowing through them can be made the same to avoid current concentration. Even in this case, since the transformers T1A and T1B are supplied with the same primary side voltage and input current, the secondary side output voltages can be made equal. Therefore, the reliability of the transformer connection circuit and the discharge tube lighting circuit can be improved.

  In the present embodiment, the transformers T2A to T2D connected to the independent electrodes are also configured to have a plurality of primary coils, and the total winding length of the primary coils is the same in the same manner as the transformers T1A and T1B. It is good also as a structure connected between each transformer T2A-T2D so that it may become. In this way, the transformers T2A to T2D connected to the independent electrodes can also accurately set the inductance value and DC resistance value of each coil to predetermined values.

  Next, the circuit configuration of the discharge tube lighting circuit according to the fourth embodiment of the present invention will be described with reference to FIG. Here, a discharge tube lighting circuit for lighting two U-shaped discharge tubes with three transformers is shown.

  In this embodiment, the discharge tube lighting circuit is configured by using two types of laminated transformers having different product numbers. Specifically, transformers T1A, T1B, and T1C configured by two primary coils and one secondary coil are used. The transformers T1A and T1C have the same product number and the same configuration, and the transformer T1B. Are larger in wire diameter and core cross-sectional area of the secondary coil NS than the above.

  The backlight 61 is used in a liquid crystal display device, and includes U-shaped discharge tubes 62A and 62B and a discharge tube lighting circuit 65. The discharge tube lighting circuit 65 is an inverter provided on the mounting board, and generates an AC voltage having a predetermined frequency from a DC voltage supplied from a power source (not shown) of the electronic device. The discharge tube lighting circuit 65 includes capacitors C1A to C1C, transformers T1A to T1C, and a switching circuit 70.

  The transformers T1A to T1C constitute the transformer connection circuit of the present invention. The specific detailed configuration of the transformers T1A to T1C is the same as that of the transformer shown in the first embodiment. The primary side coil NP1 provided in the inner layer has a small winding diameter, and the primary side coil NP2 provided in the outer layer has a large winding diameter, and the winding length becomes longer in the order of the primary side coils NP1 and NP2. . In this transformer, each coil can be wound in a state where there is no collapse or turbulence, and the winding diameter and winding position of each coil can be accurately set to a predetermined value. Accordingly, the winding length of each coil can be accurately set to a predetermined value, and the inductance value and DC resistance value of each coil can be set to a predetermined value accurately.

  Here, the primary coils NP1 of the transformers T1A and T1C are connected in parallel to each other, and the primary coils NP2 are connected in parallel, and the parallel circuit of the primary coils NP1 of the transformers T1A and T1C is connected to the primary side of the transformer T1B. The coil NP2 is connected in series and connected to the switching circuit 70. In addition, a parallel circuit of the primary side coils NP2 of each of the transformers T1A and T1C is connected in series to the primary side coil NP1 of the transformer T1B and is connected to the switching circuit 70. Note that the polarities of the primary coils are aligned.

  A schematic circuit according to this connection configuration is shown in FIG. In this figure, the winding lengths of the primary side coils NP1 and NP2 of the transformer T1A are expressed as T1A (NP1) and T1A (NP2), respectively. The winding lengths of the primary side coils NP1 and NP2 of the transformer T1B are denoted as T1B (NP1) and T1B (NP2). The winding lengths of the primary side coils NP1 and NP2 of the transformer T1C are denoted as T1C (NP1) and T1C (NP2).

  In this connection configuration, the primary coil NP1 of the transformer T1A and the primary coil NP2 of the transformer T1B form a first current path. Further, the primary side coil NP1 of the transformer T1C and the primary side coil NP2 of the transformer T1B form a second current path. The primary side coil NP2 of the transformer T1A and the primary side coil NP1 of the transformer T1B form a third current path. Further, the primary side coil NP2 of the transformer T1C and the primary side coil NP1 of the transformer T1B form a fourth current path.

Here, when the transformer T1B has the same primary coil configuration as the transformers T1A and T1C, the winding length of each primary coil satisfies the relationship of the following equation.
T1A (NP1) = T1B (NP1) = T1C (NP1) = Lnp1
T1A (NP2) = T1B (NP2) = T1C (NP2) = Lnp2
Therefore, the total winding length L of the primary coil included in each current path is expressed by the following equation.
L = T1A (NP1) + T1B (NP2)
= T1C (NP1) + T1B (NP2)
= T1A (NP2) + T1B (NP1)
= T1C (NP2) + T1B (NP1) = Lnp1 + Lnp2
Thus, the total winding length L of each current path is equal. Since each current path has the same wire diameter and the same total winding length, the voltage and current on the primary side of the transformers T1A and T1C are equal, the same current of the same voltage flows, and the output on the secondary side It becomes uniform.

When the transformer T1B has a primary coil configuration with a wire diameter, winding diameter, and number of turns different from those of the transformers T1A and T1C, the winding length of each primary coil satisfies the relationship of the following equation.
T1A (NP1) = T1C (NP1) = Lnp1A
T1A (NP2) = T1C (NP2) = Lnp2A
T1B (NP1) = Lnp1B
T1B (NP2) = Lnp2B
Therefore, the total winding length L1 of the primary coil included in the first and second current paths is expressed by the following equation.
L1 = T1A (NP1) + T1B (NP2)
= T1C (NP1) + T1B (NP2) = Lnp1A + Lnp2B
Further, the total winding length L2 of the primary coil included in the third and fourth current paths is expressed by the following equation.
L2 = T1A (NP2) + T1B (NP1)
= T1C (NP2) + T1B (NP1) = Lnp2A + Lnp1B
Thus, the total winding length L1 of the first and second current paths is equal. Further, the total winding length L2 of the third and fourth current paths is equal. Since the first and second current paths have the same inductance value and the same total resistance value, the voltage and current of the primary side coil NP1 of the transformers T1A and T1C are equal. In addition, since the third and fourth current paths have the same inductance value and the same total resistance value, the voltage and current of the primary side coil NP2 of the transformers T1A and T1C are equal. Since the voltages and currents of the primary side coils NP1 and NP2 of the transformers T1A and T1C become equal, the outputs on the secondary side of the transformers T1A and T1C become uniform.

  In this case, the total winding length L1 of the first and second current paths is different from the total winding length L2 of the third and fourth current paths, but the lines of the primary side coils NP1 and NP2 of the transformer T1B are different. By setting the diameter, the total inductance value and the total resistance value of each of the first to fourth current paths can be made equal.

  The present invention is not limited to the transformer connection circuit configured as described above, and can be implemented using various forms of transformer connection circuits. In addition, various forms of transformers can be used. Here, FIG. 8 shows a structural example of a transformer T3 having another configuration capable of implementing the present invention. FIG. 8A is an overview of the transformer T3, and FIG. 8B is a cross-sectional view of the transformer T3.

  The transformer T3 includes an I-shaped magnetic core 211A and an E-shaped magnetic core 211B. The E-shaped magnetic core 211B has a size in which the center magnetic leg of the three magnetic legs is short, and the magnetic legs at both ends are longer than the center magnetic leg. Of the three magnetic legs of the E-shaped magnetic core 211B, the magnetic legs at both ends are brought into contact with the side surfaces of the I-shaped magnetic core 211A to form magnetic paths, respectively. Tubular bobbins 212A and 212B are inserted. A primary coil NP1 and a primary coil NP2 are wound around the bobbin 212A. A secondary coil NS is wound around the bobbin 212B. The primary side coil NP1 and the primary side coil NP2 wound around the bobbin 212A are each formed by winding a single conductor wire on the bobbin 212A in a single layer, on the layer of the primary side coil NP1. The primary coil NP2 is provided with a layer. Each of the primary side coils NP1 and NP2 has the same wire diameter and number of turns, the primary side coil NP1 provided in the inner layer is small, and the primary side coil NP2 provided in the outer layer is large. It is. Therefore, the winding length of the primary side coil NP1 is short, and the winding length of the primary side coil NP2 is long. In this transformer T3, the primary side coil is individually wound around each layer of the bobbin 212A, so that each coil can be wound without being collapsed or disturbed, and the winding diameter and winding position of each coil can be accurately determined. It can be made predetermined. Accordingly, the winding length of each coil can be accurately set to a predetermined value, and the inductance value and DC resistance value of each coil can be set to a predetermined value accurately. The secondary coil has the same number of multiple turns as the plurality of primary coils NP1 and NP2 provided on the bobbin 212A on the bobbin 212B (here, it is a double turn, but the number of turns is changed in accordance with the discharge tube to be connected. ).

  Of the three magnetic legs arranged in the magnetic core 211B, the central magnetic leg 215 is the magnetic force between the primary side coils NP1 and NP2 provided on the bobbin 212A and the secondary side coil NS provided on the bobbin 212B. This is a magnetic leg for adjusting the coupling. The smaller the gap, the weaker the magnetic coupling between the primary side coils NP1 and NP2 and the secondary side coil NS.

  Even if the transformer T3 having such a configuration is used in place of the transformer T1 of each of the above-described embodiments, the present invention has the same effects, and a transformer having a configuration in which a plurality of primary coils are wound in multiple layers. If so, it can be implemented.

  In addition, the number of primary side coils constituting the series coil circuit is not limited to two, and the number of primary side coils (eg, one primary side coil of more transformers) may be increased. The present invention can be implemented, and the present invention can be implemented even in a configuration in which, for example, each layer of the primary side coil is multiplexed (for example, each primary side coil is double wound) and wound. .

It is a circuit diagram explaining the circuit structure of the conventional backlight. It is a block diagram explaining the structure of the conventional transformer. It is a figure explaining the circuit structure of the discharge tube lighting circuit of 1st Embodiment, and the structure of a transformer. It is a wave form diagram explaining the output voltage waveform of the discharge tube lighting circuit of 1st Embodiment. It is a circuit diagram explaining the structural example of the discharge tube lighting circuit of 2nd Embodiment. It is a circuit diagram explaining the structural example of the discharge tube lighting circuit of 3rd Embodiment. It is a wave form diagram explaining the output voltage waveform of the discharge tube lighting circuit of 3rd Embodiment. It is a circuit diagram explaining the structural example of the discharge tube lighting circuit of 4th Embodiment. It is a block diagram explaining the structural example of another transformer.

Explanation of symbols

1, 21, 41, 61, 101, 201-backlights 2, 22, 42, 62, 102, 202-U-shaped discharge tubes 3, 23, 43, 63, 103, 203-I-shaped discharge tubes 4, 24, 44, 64, 104, 204-power supply terminals 5, 25, 45, 65, 105, 205-discharge tube lighting circuits 6, 26, 46-series coil circuits 7, 27, 47-transformer connection circuit 10, 30, 50, 70, 110, 210-switching circuit 11, 211-magnetic core 12, 212-bobbin 12A, 12B-winding region 15-partition 48, 68-connector 215-magnetic leg C1-capacitor NP-1 Secondary side coil NS-2 Secondary side coil T1, T3-Laminated transformer T2-Conventional transformer I1, I2, I3-Current V1, V2, V3-1 Primary side voltage Va, Vb, Vc Secondary side Power Voltage

Claims (3)

A plurality of coils are wound from the inner layer to the outer layer so that each coil forms a layer in the first winding region of the magnetic core, and a coil other than the plurality of coils is connected to the second core of the magnetic core. Equipped with a plurality of laminated transformers wound around the winding area,
A coil sequentially selected from the inner layer side or the outer layer side of the first winding region of the first laminated transformer, and the first laminated transformer from the outer layer side or the inner layer side of the first winding region of the second laminated transformer And a plurality of series coil circuits in which the coils selected in reverse order are connected in series, and the total winding lengths of the coils included in each are configured to be equal,
A transformer connection circuit in which the plurality of series coil circuits are connected in parallel . A discharge tube lighting circuit comprising the transformer connection circuit according to claim 1 and a switching circuit,
The plurality of series coil circuits of the transformer connection circuit are respectively connected in parallel to the switching circuit, and the coils wound around the second winding region of the first laminated transformer and the second laminated transformer are , A discharge tube lighting circuit connected to each discharge tube terminal. Electronic apparatus provided with a discharge tube lighting circuit according to the transformer connection circuit or claim 2 of claim 1.

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